Pressure lubrication to apex corner seal

ABSTRACT

A rotary internal combustion engine of the Wankel type is disclosed. The engine has at least one epitrochoid chamber with flat side walls and an associated triangulated rotor cooperatively defining a plurality of variable volume chambers. An oil metering apparatus is integrated into the rotor for directing a jet or reservoir of oil, preferably fed from a high pressure supply, against the side walls of the housing. The apparatus employs a biased plunger to distribute a controlled oil film about the housing side walls in cooperation with the eccentric path of the selected plunger location, preferably remote and independent from the dynamic seal grid system. The oil film is pumped by action of arcuate or annular side seal strips to migrate and coat intermetallic contact surfaces of the variable volume chambers. Oil consumption is reduced while providing a functional film at predetermined locations.

United States Patent 1191 Ernest et al.

[ Oct. 21, 1975 PRESSURE LUBRICATION TO APEX CORNER SEAL [73] Assignee: Ford Motor Company, Dearborn,

Mich.

22 Filed: Aug. 6, 1974 21 Appl. No.: 495,691

[52] US. Cl 184/65; 418/91 [51] Int. Cl. FOlM l/04 [58] Field of Search 184/65, 6.8, 6.16;

Primary ExaminerRichard J. Ap1ey Assistant ExaminerWilliam R. Browne Attorney, Agent, or FirmJoseph W. Malleck; Keith L. Zerschling [57] ABSTRACT A rotary internal combustion engine of the Wankel type is disclosed. The engine has at least one epitrochoid chamber with flat side walls and an associated triangulated rotor cooperatively defining a plurality of variable volume chambers. An oil metering apparatus is integrated into the rotor for directing a jet or reservoir of oil, preferably fed from a high pressure supply, against the side walls of the housing. The apparatus employs a biased plunger to distribute a controlled oil film about the housing side walls in cooperation with the eccentric path of the selected plunger location, preferably remote and independent from the dynamic seal grid system. The oil film is pumped by action of arcuate or annular side seal strips to migrate and coat intermetallic contact surfaces of the variable volume chambers. Oil consumption is reduced while providing a functional film at predetermined locations.

5 Claims, 8 Drawing Figures US. Patent Oct.21,1975 Sheet10f2 3,913,706

. US. Patent Oct. 21, 1975 Sheet 2 of2 3,913,706

PRESSURE LUBRICATION TO APEX CORNER SEAL BACKGROUND OF THE INVENTION Both reciprocating engine piston rings and rotary engine rotor seals must be lubricated to prevent scoring. Both rely on gas pressure to form a seal with the opposing surface and both are also spring loaded to insure contact at all times. However, the top compression ring in a reciprocating engine is backed up by another ring which is intended to trap blow-by gases that manage to leak pass; even the oil control ring makes a contribution to gas sealing in the reciprocating engine. As a result, the reciprocating engine has the benefit of a threestage gas sealing system, which is not feasible in the rotary engine. The rotary engine can have only one seal at the various points that it must make an effective seal; apex seals, side seals and corner seals cannot be backed up by a second line of seals. Therefore, the necessity for an adequate and controlled amount of lubrication to assist and promote a good sealing function at each of the mechanical seals is of utmost importance.

The prior art process of lubricating the gas sealing elements of a rotary engine has been fundamentally of two types: (a) external metering to mixture added for combustion, and (b) oil premixed with the fuel. Early commercial type rotary engines have utilized oil premixed with the fuel and have used proportions of approximately 50:1 or 100:1. Actually there was little need to mix oil with the fuel, because the rotors were cooled by internal oil flow and there was considerable oil leakage from the rotor which seemed to be sufficient for lubricating the seals in the working surface. Despite the presence of lubricating oil, a symmetrical wear of the apex seal tips occurred and chatter marks appeared on the trochoid chamber wall. Seal tip wear is first and foremost a matter of material capability, but it was determined by extensive research that material capability did in fact exist. Therefore, the problem related to an inadequate lubricating film maintained under all conditions of operation and under a full cycle as the rotor moved past various stations of the epitrochoid surface. Obviously, reasonable seal life cannot be expected without lubrication of the high speed metalto-metal interfaces. The oil fuel mixture method would have worked if the necessary amount of oil had not been in constant proportion to the fuel flow. Accordingly, this method has been rejected as unsuitable for modern automobile engines.

The second method has been developed to a commercial degree, however, by supplying the necessary amount of oil to the intake port according to engine operating conditions. This method is not entirely satisfactory since it provides an excessive amount of oil which becomes waste in undue amounts as it is burned by the engine. There is little assurance that the oil film will be at all times at the points required for the metal-to-metal surface sealing.

It has been suggested by some authors, representative of the prior art, that an automatic metering of lubricating oil from the rotor side might be feasible. This has not been developed satisfactorily or implemented by the prior art since it was thought that this approach would require a separate metering pump and by the likelihood of interruption of the sealing elements by necessary limitations of introducing the oil.

The problem, therefore, still remains as to how to provide an efficient, low cost oil lubricating system for the various dynamic sealing stations of rotary engine, the system being desirably self-metering and will provide precisely the right amount of oil at the right locations, neither too much nor too little.

SUMMARY OF THE INVENTION A primary object of this invention is to provide an apparatus which is effective to distribute lubrication oil in the form of a thin smeared film between the side housings and rotor whereby a self-metering effect may be accomplished, resulting in a predetermined and precisely controlled supply of oil at required sealing interfaces.

Still another object of this invention is to provide an apparatus which eliminates the necessity for a separate oil pump for the seal lubrication function, and which draws oil from that which has been injected to the rotor bearing under high pressure.

Yet still another object, in conformity with the above objects, is to provide a unique combination of structural elements whereby the side sealing rings or strips mounted on the rotor are arranged and utilized to effect a pumping action of the oil film introduced radially inward thereof.

Yet still another object is to provide an oil metering apparatus for lubricating the dynamic seal points of a rotary engine, the apparatus utilizing an independent plunger biased to maintain a predetermined rubbing force against the side housing while being carried by the rotor, the plunger having a recess in its end face, the recess being in communication both with a high pressure oil source and with the rotor oil gallery useful in cooling the apex seal construction. The recess of the plunger converts high pressure oil to low pressure at the point of smearing the oil film between the side housing and rotor.

SUMMARY OF THE DRAWINGS FIG. 1 is a fragmentary view of the rotor and adjacent trochoid wall for a rotor internal combustion engine; said view being an elevation of the fragmentary structure of FIG. 2;

FIG. 2 is a sectional view of a rotor and rotary engine housing embodying the principles of this invention;

FIGS. 3 and 4 are views respectively similar to FIGS.

1 and 2, but illustrating an alternative embodiment.

FIGS. 5 and 6 are again views respectively similar to FIGS. 1 and 2, but illustrating still another alternative embodiment.

FIGS. 7 and 8, respectively, are three dimensional graphs comparing oil economy for a rotary engine equipped with prior art oil metering and a rotary engine equipped with oil metering of this invention.

DETAILED DESCRIPTION Turning first to FIGS. 1 and 2, a preferred embodiment is shown. The apparatus is useful in generating a controlled lubricant film along the opposed housing side walls; the film acts as a source of lubricant for coating the various dynamic sealing elements, such as a seal grid system 15 carried by the rotor. A typical rotary internal combustion engine has a principal chamber defined by opposed side walls 10 and 11 of the housing and delimited peripherally by a wall 12 preferably formed with an epitrochoid configuration. A rotor I3 is mounted for planetary movement within the chamber defined by said walls and has flat sides 8 and 9 arranged adjacent and parallel to the walls 10 and 11 of the chamber and has a triangulated outer periphery a bearing 14 supports the inner surface of the rotor upon an eccentric carried by an eccentric shaft of the engine (not shown).

The seal grid system 15, carried by the rotor, is effective to dynamically seal between the rotor and walls of said principal chamber to define a plurality of variable volume chambers such as 24. The seal grid system may comprise a sealing strip 18 carried in a slot 21 at the apices of the triangulated rotor, a cylindrical corner or end button seal 19 is carried adjacent the extreme ends of the strip 18 for sealing between the ends of the strip and the opposed side walls of the chamber. Arcuate side sealing strips, such as 16 and 17, extend between the cylindrical corner button seals 19 to complete said dynamic gas-tight seal grid which divides the space entrained by the outer portion-of the rotor and the chamber walls into said plurality of variable volume chambers. The rotor turns as shown by arrow in FIGS. 1, 3 and 5.

A primary oil cooling circuit is typically employed to conduct oil to the rotor; high pressure oil is jetted to an opening along one side of the interior periphery (not shown) and is scooped by a structure on the interior of the rotor to fling such oil throughout the interior of the hollow rotor, particularly against the radially outer wall of the rotor for cooling the apex seal assembly. Such oil cooling circuit is supplied with high pressure oil from a suitable source, but becomes low pressure when jetted into the interior of the rotor. A pair of concentric oil rings 39 and 40 are disposed in complimentary grooves in the sides of the rotor and are adapted to retain the flood of high pressure oil which resides radially inwardly thereof; such oil rings operate against the side walls 11 and 10 of the housing.

As shown in FIGS. 1 and 2, the lubrication means 30, for imparting a controlled and self-metering oil film to the side walls 10 and 11 and the various dynamic seal elements carried by the rotor, is located remotely and independently. Such lubrication means comprises a cylindrical plunger 41 at each side of the rotor and is slidably disposed in a complimentary shaped cylindrical bore 42 extending parallel to the axis of the rotor and remote from the sealing grid system. The plungers are arranged symmetrically with respect to a center plane 50 of the rotor and each have a recess 38 in its outer face adjacent a respective side wall of the rotor housing. Such recess or reservoir is supplied with oil by a path which includes an opening 31 in the rotor bearing 14in communication with the high pressure oil system carried through the eccentric shaft. The opening 31 communicates with passage 32 extending to the midsection of the plunger. An annular groove in the cylindrical periphery ofthe plunger communicates with passage 32 and also communicates with a passage 33 extending parallel to the length of the plunger leading to recess 38. Another passage 34 extends parallel to the center line of the plunger and communicates recess 38 with bore 36 in the opposite end of the plunger. The bore 36 has a helical spring 43 effective to apply a resilient force against the plunger to urge the annular face 51 of the plunger against the respective side wall (10 or 11). The bore 36 is in communication with the interior of the rotor by way of passage 37, thereby allowing oil exiting from reservoir or recess 38 to enter the low pressure oil gallery in the rotor.

In operation, a high pressure source of lubricating oil is received through opening 31 andpassages 32 and 33 to fill the reservoir or recess 38. However, the reservoir 38 will be at a relatively low pressurebecause of the the engine as the rotor advances; the film can then migrate to lubricate the seal grid and epitrochoid wall I with a decrease in oil lost through combustion. The an nular end face 51 of each plunger wil|,:by virtue of its spring bias against the side wall, reduce the supply of oil to a predetermined thin oil film. The oil film will migrate as the side sealing strips 17 come in contact with the oil during their eccentric path over the side housing surfaces 10, and 11, and will be pumped by actionof the side sealing strips, Le. 16 and17, into the variable volume chambers 24 for supplying a limited and appropriate amount of lubricant to coat the apex seal strips 18 as well as the cylindrical corner seals 19. The side sealing strips 17 promote a pumping action due to the.

eccentric motion of the rotor. No separate oil pump is necessary for the lubrication means 30.

The increase in oil economy resulting from this invention is rather direct when FIGS. 7 and 8 are viewed.

FIG. 7 illustrates the oil economy in terms of miles per quart of oil realized while operating with a conventional prior art seal grid system and a conventional oil system whereby lubricant is supplied as a mixture me tered to the induction system. FIG. 7 is a threedimensional block diagram showing induction system pressure in terms of inches per mercury plotted along one of the base lines, r.p.m. of the engine plotted along another of the base lines, and oil economy in terms of miles per quart is plotted along the vertical dimension.

FIG. 7 represents relatively poor oil economy and is that realized by a commercially available mode. At 12 inches of mercury (high pressure) and a low r.p.m. oil consumption reaches as high as 2,400 miles per quart. This is its maximum oil economy and all other combinations of pressure and speed result in much lower oil economy.

In FIG. 8, oil economy is plotted using the present invention. Maximum or peak oil economy is realized at somewhere around 10 inches of mercury at a speed of approximately 3,200 r.p.m.; a major portion of the various other combinations retain high oil economy in excess of that realized by the prior art construction. Only in the limited combinations of low pressure and high speeds, is oil economy somewhat similar.

With the use of the structure of the preferredmode,

the oil economy should be at least equal to that of the i I reciprocating engine (which obtains approximately 2000 miles per quart) under all combinations of pres sure and speed. Prior art rotary internal combustion engine constructions, such as shown in FIG. 7, have obtained approximately 800-900 miles per quart. It is expected that some of the oil lubricant will be consumed in the rotary combustion process and therefore the theoretical optimum of 5000miles per quart cannot be practically obtained in a rotary internal combustion engine. However, by use of the self-metering plunger mechanism of this invention, a much greater oil economy results in a higher performance for the seal grid system is obtained and is in excess of 1000 miles per quart.

An alternative embodiment is illustrated in FIGS. 3 and 4. Here the lubrication means is incorporated integrally with the corner seal or cylindrical button 60. Low pressure oil is received from that which is circulating within the interior of the rotor and is communicated by way of a central drilled passage 62 entering upon a semi-circular recess 61 in the end face of the corner seal 60. The corner seal is stepped in configuration for fitting within a stepped bore 63 in each side of the rotor; the stepped bore has a first portion 63a which is adapted to receive the neck 60a of the corner button and has an enlarged portion 63b for receiving the outer exposed portion of the sealing button. Annular seal rings 64 and 65 fit within annular grooves on each of the respective stepped portions 60 and 60a; seal ring 64 has a deviated portion 64a to accommodate the interposition of slot 71. Although not shown, springs bias the buttons 60 into engagement with the housing side walls. Oil is directed, by way of the location of the reservoir or recess 61, to the housing side walls at a location immediately beneath and adjacent the slot 71 containing the apex seal strips 70. This reduces, somewhat, control of the side seal arcuate strips 67 and 68 to pump a uniform film for distribution to the variable volume chambers; there is a greater opportunity for the oil, distributed by the reservoir, to migrate past the corner seal button in an excessive or in a deficient amount that is not self-metered continuously and accurately, but operable. However, the oil supply to the recesses 61 requires less fabrication. The passage 62 serves as an input to recess 61 at low oil pressures, thereby not requiring a relief passage for return of oil to the oil gallery; note that oil is obtained close to the radially outermost section of the oil gallery where oil will be urged by rotary motion to enter passage 62.

The alternative mode of FIGS. 3 and 4 shows an end face 66 which has a greater surface area for smearing and effecting a thinning out of the oil film exposed to the interior side walls of said engine. The lack of a high pressure oil feed necessitates a greater contact surface for mechanically spreading the oil film.

A second alternative embodiment is shown in FIGS. 5 and 6 and is a hybrid of the structures of FIGS. 1 and 3, but additionally incorporates an enlarged diameter for the oil reservoir or recess 82 in the corner seal or button. The use of a high pressure feed to the recess 82 is used with a return passage to the oil gallery; the oil metering is integrated as part of the corner seal and is not independent. In some particularity, the large diameter corner seals 80 have a stepped configuration whereby a neck 80a fits slidably within a stepped portion 81a of a complimentary bore. An enlarged portion 80b of the corner seal slidably fits within a larger stepped portion 81b of the bore, portion 80b overlapping and surrounding a portion of the ends of the apex seal slots 82. The corner seals have a totally circular and enlarged recess 82 which is fed with high pressure oil by way of a series of passages: 83 extending along the centerline of the corner seal, radiating passage 84 communicating by way of passage 85 with the high pressure oil supply at the rotor bearing 86. The other radiating passage 87 communicates with an angled passage 88, together serving as a return of oil to the oil gallery. Each stepped corner seal button is biased by a spring 89 extending between a centering journal on the interior of the stepped button and the opposite side of the interior of the rotor. Again, the side seal or compression strips 91 and 92, as shown, connect with the corner seal button and in a manner in which to provide effective sealing with the rotor rotating in the direction as shown by the arrow of FIG. 5.

We claim as our invention:

1. For use in a rotary internal combustion engine, the combination comprising:

a. a housing provided with a peripheral wall and opposed side walls,

b. a rotor carried within said housing for planetary movement and having an interior gallery and an axis of movement,

. sealing elements carried by said engine for providing a dynamic gas-tight seal between said rotor and said peripheral wall and side walls, said elements cooperating to complete a plurality of variable volume chambers between said rotor and housing, and

d. lubrication means carried symmetrically by said rotor with respect to a radial plane bisecting said rotor, said means directing a supply of oil toward and eccentrically onto said opposed side walls substantially with said variable volume chamber for promoting a thinly controlled smeared film of lubricant across at least a portion of said opposed side walls substantially within said variable volume chambers to improve the dynamic sealing function of said sealing elements.

2. The apparatus combination as in claim 1, in which said lubrication means comprises a spring biased plunger carrying a shallow reservoir of low pressure oil adjacent each of said opposed side housing walls, said plunger being effective to smear said oil upon said opposed side housing walls in a thinly controlled film.

3. The apparatus combination as in claim 2, in which said engine has a lubricating circuit effective to supply oil to the interior gallery of said rotor, said rotor having means for scooping oil supplied to a radially inner portion thereof and flinging said oil radially outwardly along the interior of said rotor as part of said another lubricating circuit, said lubrication means being supplied with high pressure oil from said oil circuit and having passages for separately conducting oil to said plunger reservoir, said plunger having means to circulate a portion of the oil received from said circuit back to said lubricating circuit.

4. The apparatus combination as in claim 1, in which said rotor is triangulated and said elements comprise apex seal strips carried at the apices of said rotor, corner seal buttons carried at the ends and surrounding the ends of said seal strips, and arcuate side sealing strips extending between said corner seal buttons, said lubrication means having a plunger biased to carry an oil reservoir adjacent said opposed side walls, said plunger being located remote from said elements but within the envelope of said variable volume chambers, and having means to smear said lubricant in a manner to supply a sufficient quantity of lubricant film about each of said elements during operation of said engine.

5. The combination as in claim 1, in which said lubricating means is additionally symmetrical about said axis of said rotor. 

1. For use in a rotary internal combustion engine, the combination comprising: a. a housing provided with a peripheral wall and opposed side walls, b. a rotor carried within said housing for planetary movement and having an interior gallery and an axis of movement, c. sealing elements carried by said engine for providing a dynamic gas-tight seal between said rotor and said peripheral wall and side walls, said elements cooperating to complete a plurality of variable volume chambers between said rotor and housing, and d. lubrication Means carried symmetrically by said rotor with respect to a radial plane bisecting said rotor, said means directing a supply of oil toward and eccentrically onto said opposed side walls substantially with said variable volume chamber for promoting a thinly controlled smeared film of lubricant across at least a portion of said opposed side walls substantially within said variable volume chambers to improve the dynamic sealing function of said sealing elements.
 2. The apparatus combination as in claim 1, in which said lubrication means comprises a spring biased plunger carrying a shallow reservoir of low pressure oil adjacent each of said opposed side housing walls, said plunger being effective to smear said oil upon said opposed side housing walls in a thinly controlled film.
 3. The apparatus combination as in claim 2, in which said engine has a lubricating circuit effective to supply oil to the interior gallery of said rotor, said rotor having means for scooping oil supplied to a radially inner portion thereof and flinging said oil radially outwardly along the interior of said rotor as part of said another lubricating circuit, said lubrication means being supplied with high pressure oil from said oil circuit and having passages for separately conducting oil to said plunger reservoir, said plunger having means to circulate a portion of the oil received from said circuit back to said lubricating circuit.
 4. The apparatus combination as in claim 1, in which said rotor is triangulated and said elements comprise apex seal strips carried at the apices of said rotor, corner seal buttons carried at the ends and surrounding the ends of said seal strips, and arcuate side sealing strips extending between said corner seal buttons, said lubrication means having a plunger biased to carry an oil reservoir adjacent said opposed side walls, said plunger being located remote from said elements but within the envelope of said variable volume chambers, and having means to smear said lubricant in a manner to supply a sufficient quantity of lubricant film about each of said elements during operation of said engine.
 5. The combination as in claim 1, in which said lubricating means is additionally symmetrical about said axis of said rotor. 